GB1161347A - Improvements in or relating to apparatus comprising Capacitative Stores for Electrical Energy - Google Patents

Abstract

1,161,347. Pulse generating circuits. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 2 Oct., 1967 [21 Oct., 1966], No. 47424/66. Heading H3P. [Also in Division H1] A pulse generator comprises at least one capacitive energy store comprising at least two electrodes 15, 19 having the space between them filled with a polar liquid of high dielectric constant the configurations of said electrodes being such that when a voltage is applied between them a greater electric field exists at the surface of one electrode 19 than at the other 15, the capacitive energy store being charged such that the one electrode 19 is negative relative to the other 15. When so polarized, the breakdown voltage may be several times that pertaining when the polarity is reversed. The differential electric field may be obtained by shaping the electrodes so as to present different surface areas to one another e.g. as shown, or by use of concentric construction (Fig. 1, not shown) or by having a common planar or I-section electrode, co-operating with a rod on either side (Figs. 4-7, not shown). Alternatively, plane electrodes of equal area may be employed each associated with a dielectric liquid of different conductivity or dielectric constant, the two liquids being isolated by a plastic film parallel to the electrodes. The dielectric liquid may be deionized water, ethylene glycol, glycerine or a lower alcohol, having dielectric constants in the range 81-20. A continuously operating ion exchanger can be included so as to maintain the water at low conductivity. Delay line. construction.-The capacitive store shown may take to the form of a pair of delay lines 15, 18, 19 having a common electrode 15 formed of methyl methacrylate sheathed with copper foil of specified dimensions. Part 25 of electrode 18 is shaped so as to form with electrode 15 a liquid filled spark gap. The two delay lines are preferably connected as a Blumlein modulator and are charged from a Marx pulse generator 26 via a brass tube 27 enclosed in methyl methacrylate 28, the field at the air/ water interface being reduced by a polyethylene collar 29. The delay lines are housed in a methylmethacrylate tank 12 containing deionized water and are coupled via matching devices 21, 21<SP>1</SP> to an X-ray tube 22 of the type described in Specification 1,084,014.